ISR 4331 Voice Gateway Unable to call due to external incoming noise

[Translator]

Hi,

I have been using E1 PRI configuration on ISR 4331. 

When receiving from outside, noise has been generated so badly, making a call unavailable from a month ago. 

There is no problem when sending outside, it only happens when receiving.

If both incoming and outgoing cause the same problem (using E1 PRI one line for both incoming and outgoing), it may be considered as a Network-clock issue, but it only occurs when receiving.

The carrier said that it was not the issue of them, so I replaced E1 card & ISR 4331 first, and changed the OS, but still have the same problem. 

I don't think it's a HW issue. What would cause the problem?

Attached version and config. I deleted the sensitive part in the conpig. 

If you had have the same issue, please advise me. 

Thank you. 

[Nithin Eluvathingal]

use show controller e1 to see if there is any errors on the line.

Most ISP will say that everything okay from there end.

if there are errors on the line customer might need to work with the backed switching team.